Sending humanitarian aid to Yemen does not help, actually it has very high probability to prolong the struggle.
Sending immediately military aid to Ukraine has high probability to end the conflict and avoid larger humanitarian catastrophe.
It took me some time to figure out between who is the conflict in Yemen, and why, though involvement of Saudi-Arabia and Iran was a big give away. So it is indeed between Sunny and Shia Muslims. They all appear to be Arabs in large part, so it indeed is just difference in minor details of faith. But why? It appears that it is over control of natural resources. Both sides want to have full control and leave other side nothing. In fact it is just continuation of the previous Yemen civil war.
The war was started by Shia Muslims. The conflict is 8 year old by now and it appears to be in some sort of stalemate.
I have no idea if the diplomatic solution is possible at the moment. As it is civil war, neither side has in principle more right to win.
Should we fear consequences of one side losing? I don't know, is there risk of ethnic cleansing that could follow?
Should we fear consequences of one side winning? Perhaps. If Shias win, it would mean that they copy the same conflict elsewhere, for example in Iraq. I don't know.
Most important part here in comparison with Ukraine is that these conflicts are not comparable and solutions to these conflicts will be completely different.
One is civil war and another is full scale foreign invasion with the goal to end statehood of the victim.
It is also very clear that if Ukraine would win, the conflict will be over. There would be no large scale humanitarian crisis because neighboring countries would manage to provide enough help to avoid it. There will be probably some amount of repressions against the losing side but these would be reasonable and in accordance to accepted civil practices.
It is also very clear that if Russia would win, the conflict will just start because of very high likelihood of continuous insurgency. It is also clear that there would be large scale humanitarian crisis because Russia has already stated that it will use humanitarian aid as a way to punish Ukrainians for the resistance, it is also clear that there will be large wave of repressions resulting in end of life and end of freedom on large scale.
It is also very clear that if Russia wins, it would repeat the conflict elsewhere. Most likely against NATO country.
Based on the current information, Ukraine winning is highly favorable.
Current practice has also surely demonstrated that there is at the moment no possible diplomatic solution because Russia is not accepting any except total surrender that is again not acceptable by Ukraine and is also not favorable for the overall situation.
In conclusion, conflicts in Ukraine and Yemen are very different in origin and in possible solution. Comparing these two is meaningless and does not in any way help to find resolution to either one.